The implications of subunit interactions for the structure of the T cell receptor‐CD3 complex

Publisher Website
Google Scholar
Abstract
Cell surface-expressed receptors are often multichain complexes. One of these, the T cell receptor (TcR)αβ-CD3 complex, is known to contain at least seven chains: the α and β TcR chains plus the γ, δ, ϵ and two ζ chains from the CD3 complex (αβγδϵζ2). To gain insight into the structure of the complex we have used anti-peptide antisera specific for the individual subunits of the complex, and nonionic and ionic detergents to determine subunit interactions within the complex. Four closely associated pairs of chains could be identified: αβ, ζ2, γϵ and δϵ. Interactions between the TcR αβ and either γϵ or δϵ could be observed in the apparent absence of other CD3 chains. Furthermore, a hierarchy in the strength of the association between the TcR and the individual CD3 chains could be distinguished: TcR ϵ > TcR δ > TcR γ. The ζ2 dimer could only be detected in “intact” TcR-CD3 complexes shedding no light on possible interactions with either the TcR or CD3-γ, δ and ϵ chains. Finally, cross-linking experiments suggest a close spatial relationship between the TcR αβ and both the CD3-γ and CD3-ϵ chains. The results demonstrate that the methods used give valuable information on subunit interactions in a cell surface-expressed receptor complex and suggest a TcR-CD3 complex in which two ϵ chains are present, one linked to γ and the other to δ. The data further indicate that γϵ and δϵ complexes interact directly with the TcR chains. Based on the observations a model for the structure of the TcR-CD3 is presented and discussed.